Squashed 'sglib/' changes from 367c793..07b48f5

07b48f5 Some separation of function under 'fem'
18d2737 Added comments to spatial_function stuff
b4b4b15 Fixed a bug introduced by "performance hints"
f298ee0 Moved and improved pde toolbox functions
5b2bf65 Fixed Contents.m for simplefem plus some aesthetic issues
c4ae1b7 Cleanup of fem/simplefem and related functions

git-subtree-dir: sglib
git-subtree-split: 07b48f5ca11c0a076ba64e0de5108c86c90f073c
Merge commit '04876cf87275e1f48a9960f10022a81aa9dc7ae8'

Conflicts:
	sglib/fem/simplefem/Contents.m
	sglib/fem/simplefem/clear_non_boundary_values.m
	sglib/fem/simplefem/correct_mesh.m
	sglib/fem/simplefem/find_boundary.m
	sglib/fem/simplefem/mesh_parameters.m
	sglib/fem/simplefem/refine_mesh.m